Ignore .docc files rather than emitting warnings, since it's useful to have them in packages without warnings. (#3609)

Unlike other Xcode-specific file types, such as Storyboards and Asset Catalogs, the .docc bundles are not needed for correctness during the build, and should therefore not trigger warnings.

rdar://78133445

Author: abertelrud

Sources/PackageLoading/TargetSourcesBuilder.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+ Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See http://swift.org/LICENSE.txt for license information
@@ -66,12 +66,15 @@ public struct TargetSourcesBuilder {
         self.defaultLocalization = defaultLocalization
         self.diags = diags
         self.targetPath = path
-        if toolsVersion <= ToolsVersion.v5_4 {
-            // In version 5.4 and earlier, we did not support `additionalFileRules` and always implicitly included XCBuild file types.
-            self.rules = FileRuleDescription.builtinRules + FileRuleDescription.xcbuildFileTypes
-        } else {
-            self.rules = FileRuleDescription.builtinRules + additionalFileRules
-        }
+        
+        // Configure the file rules that determine how files of various types are processed.  We always start with the builtins.
+        var fileRules = FileRuleDescription.builtinRules
+        // In version 5.4 and earlier, we did not support `additionalFileRules` and always implicitly included the XCBuild file types.
+        fileRules += (toolsVersion <= ToolsVersion.v5_4) ? FileRuleDescription.xcbuildFileTypes : additionalFileRules
+        // At the end we add the ignored types.  They might duplicate some of the rules in `additionalFileRules`, but in that case, the rule to ignore the file type will never be reached.
+        fileRules += FileRuleDescription.ignoredFileTypes
+        self.rules = fileRules
+        
         self.toolsVersion = toolsVersion
         self.fs = fs
         let excludedPaths = target.exclude.map{ path.appending(RelativePath($0)) }
@@ -253,7 +256,7 @@ public struct TargetSourcesBuilder {
     /// Returns the `Resource` file associated with a file and a particular rule, if there is one.
     private func resource(for path: AbsolutePath, with rule: Rule) -> Resource? {
         switch rule.rule {
-        case .compile, .header, .none, .modulemap:
+        case .compile, .header, .none, .modulemap, .ignored:
             return nil
         case .processResource:
             let implicitLocalization: String? = {
@@ -490,6 +493,9 @@ public struct FileRuleDescription {
 
         /// A header file.
         case header
+        
+        /// Indicates that the file should be treated as ignored, without causing an unhandled-file warning.
+        case ignored
 
         /// Sentinal to indicate that no rule was chosen for a given file.
         case none
@@ -605,6 +611,15 @@ public struct FileRuleDescription {
         )
     }()
 
+    /// File types related to DocC.
+    public static let docc: FileRuleDescription = {
+        .init(
+            rule: .ignored,
+            toolsVersion: .v5_5,
+            fileTypes: ["docc"]
+        )
+    }()
+
     /// List of all the builtin rules.
     public static let builtinRules: [FileRuleDescription] = [
         swift,
@@ -621,6 +636,12 @@ public struct FileRuleDescription {
         coredata,
         metal,
     ]
+
+    /// List of file types that are ignored in this version of SwiftPM CLI
+    /// (that don't generate warnings for being unhandled).
+    public static let ignoredFileTypes: [FileRuleDescription] = [
+        docc,
+    ]
 }
 
 extension TargetDescription.Resource.Rule {

Tests/PackageLoadingTests/TargetSourcesBuilderTests.swift

@@ -661,4 +661,38 @@ class TargetSourcesBuilderTests: XCTestCase {
 
         XCTAssertEqual(diags.diagnostics.map { $0.description }, ["found 1 file(s) which are unhandled; explicitly declare them as resources or exclude from the target\n    /Foo.xcdatamodel\n"])
     }
+
+    func testIgnoredFileTypesDoNoCauseWarnings() throws {
+        let target = try TargetDescription(
+            name: "Foo",
+            path: nil,
+            exclude: [],
+            sources: ["File.swift"],
+            resources: [],
+            publicHeadersPath: nil,
+            type: .regular
+        )
+
+        let fs = InMemoryFileSystem()
+        fs.createEmptyFiles(at: .root, files: [
+            "/File.swift",
+            "/Foo.docc"
+        ])
+
+        let diags = DiagnosticsEngine()
+
+        let builder = TargetSourcesBuilder(
+            packageName: "",
+            packagePath: .root,
+            target: target,
+            path: .root,
+            defaultLocalization: nil,
+            toolsVersion: .v5_5,
+            fs: fs,
+            diags: diags
+        )
+        _ = try builder.run()
+
+        XCTAssertTrue(diags.diagnostics.isEmpty)
+    }
 }